Spirometry can confirm the presence and severity of obstructive and restrictive lung disease. An obstructive pattern is usually seen in COPD or asthma. The response to bronchodilator can assist to differentiate asthma from COPD and is useful to assess progression and response to therapy. Restrictive pattern is seen in parenchymal disease such as pulmonary fibrosis. Extraparenchymal causes include chest wall deformity such as scoliosis, obesity, pleural effusion, and neuromuscular disorder. Spirometry is not routinely necessary in preoperative testing for non-thoracic surgery.